A Quantitative Assessment of Organic Carbon Content as a Regional Sediment-Condition Indicator.

Organic carbon content of sediments, whether directly or indirectly assessed, has often been used as an indicator of marine benthic community condition both in site-specific and regional scale condition assessment studies. The conceptual framework underlying use of this indicator was developed based primarily on site-specific studies. A quantitative analysis of literature data on sediment organic matter impacts in marine systems was conducted to determine whether biotic metrics respond to abiotic indicators of sediment organic content, as predicted by conceptual models, at larger spatial scales.

Development of an epiphyte indicator of nutrient enrichment: a critical evaluation of observational and experimental studies.

An extensive review of the literature describing epiphytes on submerged aquatic vegetation (SAV), especially seagrasses, was conducted in order to evaluate the evidence for response of epiphyte metrics to increased nutrients. Evidence from field observational studies, together with laboratory and field mesocosm experiments, was assembled from the literature and evaluated for a hypothesized positive response to nutrient addition. There was general consistency in the results to confirm that elevated nutrients tended to increase the load of epiphytes on the surface of SAV, in the absence of other limiting factors.

An evaluation of factors controlling the abundance of epiphytes on along an estuarine gradient in Yaquina Bay, Oregon, USA.

Epiphytes on seagrass () growing in the lower intertidal were examined along an estuarine gradient within Yaquina Bay, Oregon over a period of 4 years. The Yaquina Estuary receives high levels of nutrients from the watershed during the wet season and from the ocean during the dry season. Mean epiphyte biomass per unit seagrass leaf surface area (epiphyte load) peaked during the summer, and thus epiphyte load was higher during dry season than wet season in both marine and riverine dominated regions.

Assessment of spatial patterns in benthic macrofauna of the U.S. west coast continental shelf.

Aim: We assessed whether currently described marine biogeographic boundaries apply to shelf macrofauna and which environmental drivers were most associated with species differences among regions.

Location: Pacific coast of North America from the Strait of Juan de Fuca in Washington to the California-Mexico border.

Methods: Van Veen grab samples were collected from soft sediment 28-138 m deep and sieved using 1 mm mesh.

Macrophyte Community Response to Nitrogen Loading and Thermal Stressors in Rapidly Flushed Mesocosm Systems.

A mesocosm system was developed to simulate estuarine conditions characteristic of short water-residence time ecosystems of the Pacific Coast of North America, and used to evaluate the response of multiple macrophyte metrics to gradients of NO loading and temperature. Replicated experiments found that few responses could be directly attributed to NO loading up to 6 x ambient. Some response metrics exhibited weak relationships with nutrient loading but could not be resolved with available statistical power.

Patterns of shading tolerance determined from experimental light reduction studies of seagrasses.

A review and analysis of the experimental literature on seagrass shading evaluated the relationships among experimental light reduction, experimental duration, additional modifying factors and common meadow-scale seagrass response metrics to determine whether there were consistent statistical relationships. Modifying factors included study latitude, field site depth, season of experiment initiation, rhizome connectivity (severed, intact), experiment type (field, mesocosm), and seagrass life history strategy. Highly significant, best fit linear regression models were found for both biomass and shoot density reduction that included light reduction, duration and other modifying variables, although unexplained variation in the data were high.

Development of an epiphyte indicator of nutrient enrichment: threshold values for seagrass epiphyte load.

Metrics of epiphyte load on macrophytes were evaluated for use as quantitative biological indicators for nutrient impacts in estuarine waters, based on review and analysis of the literature on epiphytes and macrophytes, primarily seagrasses, but including some brackish and freshwater rooted macrophyte species. An approach is presented that empirically derives threshold epiphyte loads which are likely to cause specified levels of decrease in macrophyte response metrics such as biomass, shoot density, percent cover, production and growth. Data from 36 studies of 10 macrophyte species were pooled to derive relationships between epiphyte load and -25 and -50% seagrass response levels, which are proposed as the primary basis for establishment of critical threshold values.

A method to identify estuarine water quality exceedances associated with ocean conditions.

Wind-driven coastal upwelling along the Pacific Northwest Coast of the USA results in oceanic water that may be periodically entrained into adjacent estuaries and which possesses high nutrients and low dissolved oxygen (DO). Measurement of water quality indicators during these upwelling water entrainment events would represent extreme values for water quality thresholds derived from typical estuarine conditions. Tools are therefore needed to distinguish upwelled waters from other causes of exceedances of water quality thresholds within estuaries of the region.